Error defining relationships implementing interfaces

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1

Using following definitions in conjunction with Neo4j GraphQL Library:

interface IGraphEdge @relationshipProperties {
    created: DateTime! @timestamp(operations: [CREATE])
    modified: DateTime! @timestamp(operations: [CREATE, UPDATE])
}

interface IPerson {
    displayName: String!
    knows: [IPerson!]! @relationship(type: "KNOWS", direction: OUT, properties: "IGraphEdge")
}

type Employee implements IPerson {
    displayName: String!
    knows: [IPerson!]! @relationship(type: "KNOWS", direction: OUT, properties: "IGraphEdge")
}

type Contractor implements IPerson {
    displayName: String!
    knows: [IPerson!]! @relationship(type: "KNOWS", direction: OUT, properties: "IGraphEdge")
}

Yields the following error:

Error: Input Object type IGraphEdgeCreateInput must define one or more fields.
Input Object type IGraphEdgeUpdateInput must define one or more fields.

Adding a field to the IGraphEdge resolves the issue but is not required - I only require the created and modified date times on my basic edges.
e.g.

interface IGraphEdge @relationshipProperties {
    created: DateTime! @timestamp(operations: [CREATE])
    modified: DateTime! @timestamp(operations: [CREATE, UPDATE])
    creator: String!
    modifier: String!
}

What am I doing wrong?